•   Corrugated fiberboard

  Corrugated fiberboard is a paper-based construction material consisting of a fluted corrugated sheet and one or two flat linerboards. It is widely used in the manufacture of corrugated boxes and shipping containers. The corrugated medium and linerboard are made of paperboard, a paper-like material usually 0.010 inch, or 0.25 mm thick. Paperboard and corrugated fiberboard are sometimes called cardboard.

Manufacture of Corrugated Board

  In the classical corrugator the paper is humidified by means of high pressure steam. The humidity aims to soften the paper fibers so that the formation of the flute and the consequent gluing will go smoothly. The process adds a considerable amount of water to the papers. After the formation of the board this humidity has to be removed by drying in the so-called dry-end. Here the newly formed corrugated board is heated from the bottom by hot plates. On the top various pressures are applied by a load system on the belt.

  The corrugated medium is usually a 26 lb/1000 sq ft (127 g/m²) paperboard; higher grades are also available. It arrives to the corrugator on large rolls. At the single-facer, it is heated, moistened, and formed into a fluted pattern on geared wheels. This is joined to a flat linerboard with a starch based adhesive to form single face board. At the double-backer, a second flat linerboard is adhered to the other side of the fluted medium to form single wall corrugated board. Linerboards are often Kraft paperboard (of various grades) but may be bleached white, mottled white, colored, or preprinted.

  Common flute sizes are "A", "B", "C", "E" and "F" or microflute. The letter designation relates to the order that the flutes were invented, not the relative sizes. Flute size refers to the number of flutes per lineal foot, although the actual flute dimensions for different corrugator manufacturers may vary slightly. Measuring the number of flutes per lineal foot is a more reliable method of identifying flute size than measuring board thickness, which can vary due to manufacturing conditions. The most common flute size in corrugated boxes is "C" flute

  Corrugated fiberboard can be specified by the construction (single face, single wall, double wall, etc), flute size, burst strength, edge crush strength, flat crush, basis weights of components (pounds per thousand square feet, grams per square meter, etc), surface treatments and coatings, etc.

  The choice of corrugated medium, flute size, combining adhesive, and linerboards can be varied to engineer a corrugated board with specific properties to match a wide variety of potential uses. Double and triple-wall corrugated board is also produced for high stacking strength and puncture resistance.

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